Project Summary: The study of biologically active natural products has been a very effective gateway to the identification of compounds with unique cellular targets that have been useful both as therapeutics and,more recently in the emerging field of chemical genetics, as modulators of complex biological systems. One of the key revelations to come from molecular phylogenetic analyses of environmental samples is that only a small fraction of bacteria present in the environment is easily cultured. Traditional approaches used for the discovery of new natural products are therefore unlikely to provide access to the vast majority of natural products that exist in nature. Soil microbes that have not yet been cultured and as a result have not been examined for the production of useful natural products outnumber their cultured counterparts by at least two to three orders of magnitude. Using PCR with degenerate primers based on conserved regions in genes known to be involved in the biosynthesis of natural products and high throughput sequencing we are proposing to screen cosmid libraries of DNA extracted directly from soil for biosynthetic pathways that encode the production of new natural products. Heterologous expression will then be used to access the molecules encoded by these new gene clusters and the resulting molecules screened for biological activity in a variety of human disease related screens. Relevance: Natural products, naturally derived small organic compounds, have traditionally been one of the major sources of FDA approved therapeutics. Uncultured bacteria are one of the largest remaining pools of genetic diversity that have not yet been examined for the production of secondary metabolites. The development of methods to functionally access the previously inaccessible natural products produced by uncultured bacteria should significantly increase the number and diversity of natural products that are available to test as probes of biological processes and therapeutic agents.